Process for assembling a chiral smectic liquid crystal panel with a housing therefor

ABSTRACT

A liquid crystal apparatus includes: (a) a liquid crystal panel having a longitudinal direction and containing therein a chiral smectic liquid crystal comprising plural layers of liquid crystal molecules aligned to have a common layer normal, each layer being composed of a plurality of liquid crystal molecules, each liquid crystal molecule being oriented to one of plural stable orientation states in the absence of an electric field; and (b) a panel supporting means comprising two fixing axes which extend in parallel with the longitudinal direction of the liquid crystal panel and fix the peripheral sides of the liquid crystal panel, the fixing axes forming an intersection angle θ 1  in the range of 0-25 degrees with the common layer normal.

This application is a division of application Ser. No. 07/834,987 filedFeb. 14, 1992, U.S. Pat. No. 5,293,544, which is a continuation-in-partof prior application Ser. No. 07/813,768 filed Dec. 27, 1991 nowabandoned, which in turn is a continuation of prior application Ser. No.07/489,338 filed Mar. 6, 1990 now U.S. Pat. No. 5,109,294.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a liquid crystal apparatus for use in adisplay apparatus, a light bulb apparatus, etc., particularly such aliquid crystal apparatus using a chiral smectic liquid crystal.

Clark and Lagerwall have proposed a type of display device wherein therefractive index anisotropy of a chiral smectic liquid crystal isutilized and combined with a polarizer to control the transmission oflight therethrough (U.S. Pat. No. 4,367,924, etc.). The chiral smecticliquid crystal shows a ferroelectricity in its chiral smectic C phase(SmC*) or H phase (SmH*) and assumes a helical alignment structure inits bulk state. If the liquid crystal at a temperature yielding thechiral smectic C phase or H phase inherently providing a helicalalignment structure is disposed between a pair of substrates set to havea spacing therebetween small enough to suppress the formation of thehelical alignment structure, the chiral smectic liquid crystal is placedin a biaxial orientation state in which the liquid crystal molecule isany or either one of a plurality of optically stable states including afirst optically stable state and a second optically stable statedepending on an electric field applied thereto. The liquid crystalfurther shows a memory characteristic that the molecule retains theresultant orientation state in the absence of an electric field andshows a high-speed responsive characteristic in response to a change inelectric field, so that it is expected to be widely used in a high-speedand memory-type display device. In such an apparatus, a chiral smecticliquid crystal is composed of plural molecular layers each comprising aplurality of liquid crystal molecules and disposed vertically to thesubstrates, so that the plural molecular layer are uniformly aligned tohave a single normal which generally aligns with a rubbing axis impartedto the substrates, as disclosed in U.S. Pat. No. 4,639,089.

In this instance, in order for an optical modulation device using such achiral smectic liquid crystal in a bistable alignment state to exhibitthe above-mentioned memory characteristic and high-speed responsiveness,it is necessary that the bistable alignment state is stably anduniformly retained in the device and the device is excellent indurability.

A chiral smectic liquid crystal device in the above-mentioned bistablealignment state comprises liquid crystal molecules in a highly orderedalignment state because of the uniformity of the alignment state. Thehighly ordered alignment state of the liquid crystal molecules issusceptible to external forces applied to a cell, such as impact anddistortion, and the liquid crystal molecules under application of suchexternal forces are disordered to result in, typically, a sandedtexture. The occurrence of a sanded texture under application of animpact force has been reported by, e.g., U.S. Pat. No. 4,674,839 to A.Tsuboyama, et al.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystalapparatus having solved the above-mentioned problems, particularly aliquid crystal apparatus having a stabilized structure improved indurability against impact or distortion.

Another object of the present invention is to provide a liquid crystalapparatus having a stabilized structure capable of protecting thebistable or multistable alignment or orientation state of a chiralsmectic liquid crystal from impact or distortion.

According to the present invention, there is provided a liquid crystalapparatus, comprising:

(a) a liquid crystal panel having a longitudinal direction andcontaining therein a chiral smectic liquid crystal comprising plurallayers of liquid crystal molecules aligned to have a common layernormal, each layer being composed of a plurality of liquid crystalmolecules, each liquid crystal molecule being oriented to one of pluralstable orientation states in the absence of an electric field; and

(b) a panel supporting means comprising two fixing axes which extend inparallel with the longitudinal direction of the liquid crystal panel andfix the peripheral sides of the liquid crystal panel, the fixing axesforming an intersection angle θ₁ in the range of 0-25 degrees with thecommon layer normal.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a chiral smectic liquid crystalcell (device) used in the present invention.

FIG. 2 is a schematic perspective illustration of a molecular layerstructure used in the present invention.

FIGS. 3A and 4A are perspective views of apparatus according to thepresent invention, and FIGS. 3B and 4B are corresponding plan views.

FIGS. 5A and 6A are perspective views of apparatus outside the scope ofthe present invention, and FIGS. 5B and 6B are corresponding plan views.

FIG. 7 is a plan view of another apparatus outside the presentinvention.

FIGS. 8A, 8B and 8C are time charts showing a set of driving waveformsused in a multiplex drive scheme used in the present invention.

FIGS. 9A and 9B are microscopic photographs (x200) showing a normalalignment texture and a sanded texture, respectively.

FIG. 10 is a block diagram of an apparatus according to the presentinvention.

FIGS. 11A, 11B, 11C and 11D are time charts illustrating datacommunication between a panel and a drive circuit.

FIG. 12 is a cross-sectional view illustrating the alignment of theliquid crystal apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to our study based on experiments regarding theabove-mentioned problems, the following points have been found.

FIG. 1 schematically shows a type of a chiral smectic liquid crystalcell used in the experiments. A cell having the structure shown in thefigure was supported according to the structure of the present inventionand another structure, and the resultant apparatus were checked withrespect to their strength or durability.

Referring to FIG. 1, the cell comprises substrates (glass plates) 11aand 11b coated with transparent stripe electrodes 12a and 12b of In₂ O₃and ITO (indium tin oxide) which are covered with 200 Å to 10000 Å-thickinsulating films 13a and 13b of SiO₂, TiO₂, Ta₂ O₅, etc., and 50 Å to1000 Å-thick alignment control films 14 and 14b, respectively, ofpolyimide, polyamide, polyester, etc.

The alignment control films 14a and 14b have been respectively rubbed inthe direction of an arrow Ra (the direction of stripe electrodes 12a,i.e., the lateral direction of the drawing) and in the direction of anarrow Rb (the direction perpendicular to the direction of the stripeelectrodes 12b (extending in the direction perpendicular to the drawingsurface)). The rubbing directions Ra and Rb are parallel with each otherand in the same direction. Between the substrates 11a and 11b, a chiralsmectic liquid crystal 15 is disposed. The spacing between thesubstrates 11a and 11b is set to be sufficiently small (e.g., 0.1-3microns) as to suppress the formation of a helical alignment structureof the chiral smectic liquid crystal 15, so that the chiral smecticliquid crystal is in bistable orientation states. The above-mentionedsufficiently small spacing is held by spacer beads 16 (silica beads oralumina beads). The resultant cell structure is sandwiched between apolarizer 17a (polarizer on the backlight side) and an analyzer 17b(polarizer on the display side) disposed in right-angle cross nicols. Asdescribed above, the chiral smectic liquid crystal in this instance iscomposed of plural molecular Layers each comprising a plurality ofliquid crystal molecules and disposed perpendicularly to the substrates.The plurality of molecular layers are uniformly aligned so as to providea common normal substantially in alignment with the rubbing axis. As aresult, bistable or multi-stable orientation states are developed.

FIG. 2 is a schematic perspective view illustrating a laminar structureof a liquid crystal 21 in chiral smectic C phase. Referring to FIG. 2,the liquid crystal 21 in chiral smectic C phase comprises pluralmolecular layers 22 standing against the substrate 11a (11b) so as toprovide a single layer normal 23 to the molecular layers 22. The normal23 is generally in parallel with the rubbing directions Ra and Rb. Eachmolecular layer 22 is composed of a plurality of liquid crystalmolecules 24 in parallel with or pre-tilted with respect to thesubstrate 11a (11b).

The liquid crystal 21 in chiral smectic C phase shown in FIG. 2 isdisposed between a pair of substrates 11a and 11b spaced apart from eachother with a spacing sufficiently small (e.g., 0.5-5.0 microns) tosuppress the formation of a helical alignment structure of the Liquidcrystal, thereby developing two or more stable orientation states ofliquid crystal molecules 24 in the absence of an electric field.

The ferroelectric liquid crystal used in the present invention may bealigned to form a chevron structure as shown in FIG. 12 which providesan excellent bright state under cross nicols, thus providing asufficient contrast. Referring to FIG. 12 which is a cross-sectionalview showing an alignment state of a ferroelectric liquid crystal 123disposed between a pair of substrates 121 and 122, the liquid crystal123 forms a plurality of layers 125 each comprising plural liquidcrystal molecules 124. The layers 125 are aligned in parallel with eachother in one direction but each layer 125 is bent or folded. In thisinstance, each liquid crystal molecule contacting the substrate 121 or122 may preferably be inclined to have a pre-tilt angle θ_(a) of atleast 5 degrees, further preferably 10-30 degrees. Such an alignmentstate may preferably be provided by rubbing the substrates 121 and 122in the same direction of 126 and 127.

FIGS. 3A and 3B illustrate a liquid crystal apparatus according to thepresent invention. Referring to FIG. 3A, the liquid crystal apparatuscomprises a support structure 31 which is formed of a rigid body of,e.g., aluminum, its alloy or plastic and in turn comprises a base 311and side supports 312. The base 311 has substantially the same size asthat of the panel 1 held thereabove. Each side support 312 may have awidth on the order of 1 cm-5 cm. On the upper surface of each sidesupport 312, a rubber sheet 32 has been applied.

The liquid crystal panel 1 has the abovementioned sectional structureshown in FIG. 1 in which a liquid crystal 21 in chiral smectic C phaseshown in FIG. 2 is contained.

FIG. 3B is a schematic plan view of the apparatus shown in FIG. 3A.Referring to FIG. 3B, the liquid crystal panel 1 is so disposed that thenormal 23 to the molecular layers 22 is in parallel with the fixing axesof the side supports 312 to provide an intersection angle θ₁ =0 betweenthe fixing axis 34 and the normal 23.

In the apparatus of the present invention shown in FIG. 3A, both sidesof the liquid crystal panel 1 are placed on the side supports 312 andfixed thereat by fixing means including ordinary screws 33 and toolingmembers 35. On the liquid crystal panel 1 side of each tooling member35, a rubber sheet 36 may be attached so as to prevent breakage of theliquid crystal panel 1 at the time of the fixing operation.

FIGS. 4A and 4B show another apparatus according to the presentinvention which is identical to the one shown in FIGS. 3A and 3B exceptthat the angle θ₁ is 25 degrees.

FIGS. 5A and 5B show an apparatus outside the present invention which isidentical to the one shown in FIGS. 3A and 3B except that the angle θ₁is 90 degrees. FIGS. 6A and 6B show an apparatus outside the presentinvention which is identical to the one shown in FIGS. 3A and 3B exceptthat the angle θ₁ is 65 degrees.

FIG. 7 shows an apparatus outside the present invention which isidentical to the one shown in FIGS. 3A and 3B except that an additionalpair of side supports 71 are provided perpendicularly to the sidesupports 312 so as to fix the liquid crystal panel 1 on four sides.

As will be described in Examples appearing hereinafter, we tested theliquid crystal apparatus shown in FIGS. 3-7 by a series of impactdurability tests wherein each apparatus was subject to dropping impactsincreasing from 10G at an increment of 5G by means of a droppingdurability tester (trade name: "DT-50", mfd. by Yoshida Seiki K. K.).

As a result, the apparatus shown in FIGS. 5A and 5B caused adeterioration in alignment of liquid crystal (sanded texture) at adropping impact of 15G. FIG. 9A is a microscopic photograph (x200) ofthe alignment state of the liquid crystal in the liquid crystal panel 1of the apparatus shown in FIGS. 5A and 5B before the impact test andFIG. 9B is a microscopic photograph (x200) of the alignment state afterthe application of a dropping impact of 15G showing a sanded texture.Further, when the apparatus shown in FIGS. 6 and 7 were subjected to thesame dropping impact test, the apparatus respectively caused a sandedtexture as shown in FIG. 9B after application of a dropping impact of15G.

On the other hand, the liquid crystal apparatus shown in FIGS. 3A and 3Bwas also subjected to the same dropping impact test, whereby theapparatus did not result in a sanded texture as shown in FIG. 9B evenafter application of a dropping impact of 90G.

Hereinafter, the present invention will be explained more specificallywith reference to Examples.

EXAMPLE 1

A pair of glass plates each in a size of 200 mm×200 mm and having athickness of 1.1 mm were provided, and stripe electrodes (12a, 12b shownin FIG. 1) were respectively formed on the glass plates. On thesubstrates, 1000 Å-thick low-resistivity connection lines (13a, 13bshown in FIG. 1) of molybdenum were provided so as to stride between theITO electrodes and pixels. Further, 500 Å-thick SiO₂ layers were formedthereon by sputtering as layers for preventing short circuit between theelectrodes on both substrates. Each substrate was further coated with a0.1%-aminosilane solution in IPA (isopropanol) by means of a spinnerrotating at 2000 rpm for 15 seconds, followed by heating at 150° C., andthen coated with polyimide-forming solution ("SP-510", available fromToray K. K.) diluted to 2% with a 2:1 mixture of NMP andn-butylcellulose by means of a spinner rotating at 3000 rpm for 30 min.The coating was then heat-cured at 300° C. for 1 hour to form a 200Å-thick polyimide alignment film (14a or 14b in FIG. 1).

One (11a in FIG. 1) of the two glass substrates thus treated wassubjected to rubbing on the polyimide film (14a) after the curing in thedirection of the arrow Ra, and the other substrate (11b in FIG. 1) wassubjected to rubbing in the direction of the arrow Rb.

Then, alumina beads (16 in FIG. 1) having an average particle size ofabout 1.5 micron were dispersed on one of the glass substrates, and theother substrate was superposed thereon, so that the rubbing directionson the substrates were parallel with each other. Thus, the twosubstrates were bonded to each other to form a blank cell having a cellgap of about 1.5 microns as measured by a Bereck compensator(measurement based on phase difference). The cell was filled undervacuum with a ferroelectric liquid crystal ("CS-1014" (trade name)available from Chisso K. K.) heated into isotropic phase and thengradually cooled at a rate of 0.5° C./hour to 25° C. whereby the liquidcrystal was aligned. The experiment was thereafter conducted at 25° C.The liquid crystal "CS-1014" (trade name) showed the following phasetransition series. ##STR1## (SmA:smectic A phase, Ch.:cholesteric phase,Iso.:isotropic phase)

The liquid crystal cell thus obtained was observed through right-anglecross nicols, whereby a defect-free monodomain of chiral smectic C phasein helical structure was found to be formed.

Further, the liquid crystal device (cell or panel) was held at 60° C. toassume an alignment state in SmA phase and was observed through apolarizing microscope with right-angle cross nicol polarizers to measurethe alignment direction of the liquid crystal molecular layers byutilizing a phenomenon that the liquid crystal molecules are alignedperpendicular to the layers. More specifically, the right angle crossnicols were rotated with respect to the liquid crystal cell to find outthe darkest position where the optical axis of one of the polarizerscoincided with the layer normal 23 of the molecular layers 22.

The liquid crystal panel (cell) thus prepared was fixed to a support attwo sides thereof as shown in FIGS. 3A an 3B having an axis 34 formingan angle θ₁ =0 with the layer normal 23 in Sm*C phase to form a liquidcrystal device unit (apparatus) as shown in FIG. 3A.

The liquid crystal device unit was subjected to the above-mentioneddropping impact test, whereby alignment deterioration (sanded texture)occurred at a dropping impact of 100G but no alignment deterioration wasobserved at all at a dropping impact of 90G.

EXAMPLE 2

A liquid crystal panel (cell) was prepared in the same manner as inExample 1 except that the rubbing direction was inclined by 25 degrees.Then, the liquid crystal panel was held at 60° C. to measure thedirection of the molecular layer normal 23.

Then, the thus prepared liquid crystal was fixed to a support at twosides thereof as shown in FIGS. 4A and 4B having an axis forming anangle θ₁ =25 degrees with the layer normal 23 in Sm*C phase to form aliquid crystal device unit.

The liquid crystal device unit was subjected to the above-mentioneddropping impact test, whereby alignment deterioration (sanded texture)occurred at a dropping impact of 50G but no alignment deterioration wasobserved at a dropping impact of 40G.

COMPARATIVE EXAMPLE 1

A liquid crystal device unit was prepared in the same manner as inExample 1 except that the liquid crystal panel was fixed to a support attwo sides thereof as shown in FIGS. 5A and 5B forming an angle θ₁ =90degrees with the layer normal 23 in SmC* phase.

When the liquid crystal device unit was subjected to the above-mentioneddropping impact test, alignment deterioration (sanded texture) occurredat a dropping impact of 15G.

COMPARATIVE EXAMPLE 2

A liquid crystal panel (cell) was prepared in the same manner as inExample 1 except that the rubbing direction was inclined by 65 degrees.Then, the liquid crystal panel was held at 60° C. to measure thedirection of the molecular layer normal 23.

Then, the thus prepared liquid crystal panel was fixed to a support attwo sides thereof as shown in FIGS. 6A and 6B having an axis forming anangle θ₁ =65 degrees with the layer normal 23 in Sm*C phase to form aliquid crystal device unit.

The liquid crystal device unit was subjected to the above-mentioneddropping impact test, whereby alignment deterioration (sanded texture)occurred at a dropping impact of 15G.

COMPARATIVE EXAMPLE 3

All the periphery (4 sides) of the liquid crystal panel prepared inExample 1 was fixed to a support as shown in FIG. 7.

The resultant liquid crystal device unit caused a sanded texture at adropping impact of 15G.

Five units each of the apparatus identical to those prepared in Examples1 and 2 and Comparative Examples 1-3 were respectively provided with adropping impact of 40G, and then subjected to a display operation usinga set of driving waveforms as shown in FIGS. 8A, 8B and 8C, wherein FIG.8A shows a time-serial waveform of a scanning signal applied to ascanning line; FIG. 8B shows a time-serial waveform of data signalsapplied to a data line including "W" (white) data signal and "B" (black)data signal; and FIG. 8C shows a voltage waveform applied to a pixelformed at the intersection of the scanning line and the data line. Thedisplay operation was performed under the conditions of ΔT=50 μsec, andVa=3V₀ =21 volts.

As a result, the device units according to the types of Examples 1 and 2showed a good display operation, whereas those according to the types ofComparative Examples 1-3 could not perform a display operation.

In the apparatus of the present invention, the intersection angle θ₁ maybe effectively in the range of 0-25 degrees, but more effectively in therange of 0-15 degrees.

FIG. 10 illustrates an outline of a display apparatus including adisplay panel 100 and peripheral circuits used in the present invention.The display panel 100 comprises data electrodes DL (e.g., 640 lines),scanning electrodes SL (e.g., 400 lines) and a chiral smectic liquidcrystal hermetically disposed therebetween. The data electrodes DL aresupplied with data signals from a data electrode drive circuit 102, andthe scanning electrodes SL are supplied with data signals from ascanning electrode drive circuit 103. The data electrode drive circuit102 includes a shift register 104 receiving one line of image signaldata shown in FIGS. 11A, 11B, 11C and 11D serially supplied to bedisplayed on the display panel 100; a line memory 105 receiving inparallel and memorizing the serial data for one line sent to the shiftregister 104; and a data signal supply circuit 106 for supplying datasignals to the respective data electrodes DL according to the data forone line memorized in the line memory 105.

The scanning electrode drive circuit 103 includes an address data latch107 for latching an address signal for designating one of the scanningelectrodes SL; an address decoder 108 for selecting one of the scanningelectrodes SL according to the address signal latched by the addressdata latch 107; and a scanning signal supply circuit 109 for supplying ascanning selection signal to one scanning electrode SL selected by theaddress decoder 108.

The display apparatus further includes an image memory VRAM 113 formemorizing image data for each of the bits corresponding to the pixelsformed at the intersection of the data electrodes DL and the scanningelectrodes SL on the display panel 100; a changeover directing signalline 110 for supplying a horizontal synchronizing signal; an addressdata line 111 for transferring output signals (VRAM output signals shownin FIG. 11D) from the image memory (VRAM) 113 to the display panel 100;a changeover switch 112 for determining either the shift register 104 orthe address data latch 107 to which the VRAM output signals from theaddress data line 111 are to be sent depending on the signal (horizontalsynchronizing signal) from the changeover directing signal line 110.According to the present invention, as shown in FIG. 11D, the VRAMoutput signals include an address signal A for addressing a scanningelectrode to which a scanning selection signal is to be sent, and imagesignals B for designating data signals to be supplied to the dataelectrodes for the respective data electrodes. By the action of theswitch 112, the address signal A is transferred to the address datalatch 107, and the image signals B are set to the shift register 104.

The display apparatus further includes a CPU 114 by which the outputsfrom the image memory 113 are controlled. Particularly when partialrewriting data are generated in the image memory 114, the CPU 114 readsout the order of scanning electrodes to be addressed from the partialrewriting data corresponding to the rewriting liens and supplies theaddress signal A thereto.

Next, a signal transfer system by using the above display apparatus willbe explained.

FIGS. 11, 11B, 11C and 11D are time charts showing a directing signal110S appearing on the changeover directing signal line 110 and VRAMoutput signals 111S appearing on the address data line 111.

When the directing signal 110S is at the high level, the VRAM outputsignal 111S comprises an address signal A for designating one of thescanning electrodes SL. Thereafter, when the directing signal 110S is atthe low level, the address data line 111 serially transfers VRAM outputsignals 111S which are image signals B serially outputted in the imagesignal scanning period, i.e., data signals each corresponding to one ofthe data electrodes DL. Before the time when the changeover directingsignal 111S is at the high level again, a period called "dead time C" isplaced, which is a very short time allotted as a process time for anexternal transfer apparatus.

When the directing signal 110S is at the high level, the switch 112turns the address data line 111 over to the address data latch 107 side.As a result, the address signal A in the VRAM output signals 111S islatched by the address data latch 107, and a scanning selection signalis supplied to one of the scanning electrodes SL through the addressdecoder 108 and the scanning signal supply circuit 109.

Then, when the directing signal 110S is at the low level, the switch 112turns the address data line 111 over to the shift register 104 side. Asa result, the image signals in the VRAM output signals 111S are suppliedto the shift register 104 and sent through the line memory 105 to thedata signal supply circuit 106, from which a white data signal and ablack data signal are supplied to the respective data electrodes DLselectively depending on given data. In other words, an address signal Asent to the scanning electrode drive circuit 103 and serial imagesignals B sent to the data electrode drive circuit 102 may be suppliedto one address data line 111, so that the address signal A foraddressing a selected scanning electrode is conveyed first, andsubsequently thereafter the image signals B corresponding to theselected scanning electrode may be sent to the data electrodes. Asimilar control may be repeated for the subsequent second, third, . . ., scanning electrodes, whereby one picture may be formed.

In a preferred embodiment of the present invention, when a part of aalready formed display picture is rewritten (e.g., for correction of acharacter or a multi-window display on a display picture), theabove-mentioned address signal A may be controlled by the CPU so thatthe address signal A is supplied to only scanning electrodes in thepartially rewritten region. Further, such a partial rewriting scheme byapplying a scanning selection signal only to a selected scanningelectrode may also be applicable to a cursor display or mouse display ona display picture.

Referring again to FIGS. 11A, 11B, 11C and 11D, the directing signal110S is synchronized with the horizontal synchronizing signal HD, andthe high level of 110S is allotted to the horizontal fly-back time andthe low level thereof is allotted to the image signal scanning period,with respect to time. Further, the image data 1, 2, 3, 4, . . . , 640serially supplied in one horizontal scanning period correspond to imagedata of data signals sent to the first, second, third, fourth, . . . ,640-th data electrodes, respectively.

What is claimed is:
 1. A process for assembling a chiral smectic liquidcrystal panel with a housing therefor, comprising the steps of:(a)forming a smectic A liquid crystal between a pair of substrates eachsubjected to rubbing in one direction so that said smectic A liquidcrystal forms plural molecular layers organized by plural molecules andhaving a common layer normal thereto and each smectic A liquid crystalmolecule is oriented in a direction perpendicular to said molecularlayers thereof so that the smectic A liquid crystal provides an opticalaxis coinciding with the common layer normal; (b) forming a chiralsmectic liquid crystal by cooling the smectic A liquid crystal to achiral smectic C phase, in which the liquid crystal molecules aredisposed in plural layers having a layer normal substantially coincidingwith said one direction of rubbing, thereby providing a chiral smecticliquid crystal panel; (c) disposing two elongated supporting membersconstituting a housing in parallel with each other to have a commonlongitudinal direction; and (d) disposing the two elongated supportingmembers along sides of the substrates thereby to support the chiralsmectic liquid crystal panel, so that the longitudinal direction of thetwo elongated supporting members forms an intersection angel θ₁ in arange of 0°-25° with said common layer normal to the chiral smecticliquid crystal.
 2. A process according to claim 1, wherein theintersection angle θ₁ is in a range of 0°-15°.
 3. A process according toclaim 1, wherein the in intersection angle θ₁ is 0°.
 4. A processaccording to claim 1, wherein both of said pair of substrates arerespectively provided with an alignment axis.
 5. A process according toclaim 4, wherein the alignment axis is provided by rubbing.
 6. A processaccording to claim 1, wherein both of said pair of substrates arerespectively provided with an alignment axis in the same direction.
 7. Aprocess according to claim 6, wherein the alignment axis is provided byrubbing.